The discussion revolves around the assumptions and interpretations related to Newton's second law, particularly in the context of solving problems involving velocities and frames of reference. Participants explore the role of velocity in the application of the law, especially in specific scenarios like the rocket problem.
Participants express differing views on the relevance of velocity in Newton's second law, with no consensus reached on the necessity of expressing velocities in a specific frame for problem-solving.
There are unresolved assumptions regarding the definitions of frames of reference and the specific conditions under which velocity may or may not be considered in applying Newton's second law.
Velocity doesn't even appear in Newton's second law.kq6up said:With my understanding of Newton's second -- if I am going to use it to solve a problem, I would need to write ALL velocities in the system with respect to the lab frame (inertial rest frame) -- correct?
What, you have there is acceleration and average acceleration, which of course can be expressed in terms of velocity.kq6up said:It does in the rocket problem. ##\dot{p}=\dot{m}v+m\dot{v}=F_{thrust}##. Also, if you are calculating the the change in momentum over some time interval ##F=m\frac{\Delta v}{\Delta t}##.